The present invention relates to a method for the separation of coal from ROM coal. More particularly, it relates to a method for separating coal from slate, shale, limestone, fireclay, and boney coal present in ROM coal.
As presently mined, ROM coal contains many impurities such as slate, shale, limestone, fireclay, and boney coal in varying concentrations. These and various other impurities in the ROM coal are hereinafter referred to as refuse. Separation of the coal from the refuse is generally required for about 2/3 of all the bituminous coal mined in the United States before the coal can be economically used in an environmentally acceptable manner. Separation of coal from the refuse has been conducted through techniques such as jigging, heavy media separation, shaking tables, and hydrocyclones. These techniques are based upon differences between the specific gravities of coal and the refuse. All of these techniques require large volumes of water to achieve desired separation. Gravity separation techniques are limited where large amounts of water are not available. Efficiency of separation of these techniques decreases as the specific gravities of the coal and refuse approach each other. For example, it is difficult to separate good coal from boney coal, as there is only a small difference between their specific gravities.